Maximum Contractile Strain in the Biceps Brachii Is Bounded by Sarcomere Geometry

Skeletal muscles’ primary function is the application of force to its bony origins and insertions. There are various models of muscle function that generally assume a uniform behavior from origin to insertion during force generation even though the structure and activation is complex. Engineering strains within skeletal muscles, though, have been shown to be non-uniform [1]. We have developed methods to quantify Lagrangian finite strains using cine phase-contrast magnetic resonance imaging (CPCMRI) and post-processing algorithms [2] and have described them during cyclic motion in the supraspinatus and biceps brachii. Principal and maximum in-plane shear strains can be identified at the scale of millimeters throughout the contracting and elongating muscle.